Structure and stability of hydrogen atom adsorbed on nitrogen-doped carbon nanotubes

The adsorption process of hydrogen atom on nitrogen-doped carbon nanotube (CNT) and its effects on the electronic properties are investigated using the first-principles density-functional methods. As possible hydrogen adsorption sites, three different positions are considered to discuss adsorption energies of the hydrogen atom on N-doped (10,0) CNTs. It is found that the favorable hydrogen adsorption site on N-doped (10,0) CNT is not on top of the nitrogen atom but on top of carbon atoms next to the nitrogen atom. Interestingly, it is found that the impurity state induced by doping with nitrogen atom is shifted from conduction-band minimum to valence-band maximum by the adsorption of the hydrogen atom.